SMAD4 and neoplasm: Negative SMAD4 expression showed a significant relationship with tumour diameter (χ2 = 6.389, P = 0.016), TNM staging (χ2 = 6.303, p = 0.016), lymphatic invasion (χ2 = 74.451, P = 0.000) and differentiation (χ2 = 5.272, P = 0.039).